[PATCH v9 0/2] Support TDX guests on Hyper-V (the x86/tdx part)

[PATCH v9 0/2] Support TDX guests on Hyper-V (the x86/tdx part)

[Dexuan Cui]

The two patches are based on today's tip.git's master branch.

Note: the two patches don't apply to the current x86/tdx branch, which
doesn't have commit 75d090fd167a ("x86/tdx: Add unaccepted memory support").

As Dave suggested, I moved some local variables of tdx_map_gpa() to
inside the loop. I added Sathyanarayanan's Reviewed-by.

Please review.

FWIW, the old versons are here:
v8: https://lwn.net/ml/linux-kernel/20230620154830.25442-1-decui@microsoft.com/
v7: https://lwn.net/ml/linux-kernel/20230616044701.15888-1-decui%40microsoft.com/
v6: https://lwn.net/ml/linux-kernel/20230504225351.10765-1-decui@microsoft.com/

Dexuan Cui (2):
  x86/tdx: Retry TDVMCALL_MAP_GPA() when needed
  x86/tdx: Support vmalloc() for tdx_enc_status_changed()

 arch/x86/coco/tdx/tdx.c           | 87 ++++++++++++++++++++++++++-----
 arch/x86/include/asm/shared/tdx.h |  2 +
 2 files changed, 77 insertions(+), 12 deletions(-)

-- 
2.25.1

[PATCH v9 1/2] x86/tdx: Retry TDVMCALL_MAP_GPA() when needed

[Dexuan Cui]

GHCI spec for TDX 1.0 says that the MapGPA call may fail with the R10
error code = TDG.VP.VMCALL_RETRY (1), and the guest must retry this
operation for the pages in the region starting at the GPA specified
in R11.

When a fully enlightened TDX guest runs on Hyper-V, Hyper-V can return
the retry error when set_memory_decrypted() is called to decrypt up to
1GB of swiotlb bounce buffers.

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
---
 arch/x86/coco/tdx/tdx.c           | 64 +++++++++++++++++++++++++------
 arch/x86/include/asm/shared/tdx.h |  2 +
 2 files changed, 54 insertions(+), 12 deletions(-)

Changes in v2:
  Used __tdx_hypercall() directly in tdx_map_gpa().
  Added a max_retry_cnt of 1000.
  Renamed a few variables, e.g., r11 -> map_fail_paddr.

Changes in v3:
  Changed max_retry_cnt from 1000 to 3.

Changes in v4:
  __tdx_hypercall(&args, TDX_HCALL_HAS_OUTPUT) -> __tdx_hypercall_ret()
  Added Kirill's Acked-by.

Changes in v5:
  Added Michael's Reviewed-by.

Changes in v6: None.

Changes in v7:
  Addressed Dave's comments:
  see https://lwn.net/ml/linux-kernel/SA1PR21MB1335736123C2BCBBFD7460C3BF46A@SA1PR21MB1335.namprd21.prod.outlook.com

Changes in v8:
  Rebased to tip.git's master branch.

Changes in v9:
  Added a comment before 'max_retries_per_page'.
  Moved 'args', 'map_fail_paddr' and 'ret' into the loop.
  Added Kuppuswamy Sathyanarayanan's Reviewed-by.

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 1d6b863c42b0..746075d20cd2 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -703,14 +703,15 @@ static bool tdx_cache_flush_required(void)
 }
 
 /*
- * Inform the VMM of the guest's intent for this physical page: shared with
- * the VMM or private to the guest.  The VMM is expected to change its mapping
- * of the page in response.
+ * Notify the VMM about page mapping conversion. More info about ABI
+ * can be found in TDX Guest-Host-Communication Interface (GHCI),
+ * section "TDG.VP.VMCALL<MapGPA>".
  */
-static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
+static bool tdx_map_gpa(phys_addr_t start, phys_addr_t end, bool enc)
 {
-	phys_addr_t start = __pa(vaddr);
-	phys_addr_t end   = __pa(vaddr + numpages * PAGE_SIZE);
+	/* Retrying the hypercall a second time should succeed; use 3 just in case */
+	const int max_retries_per_page = 3;
+	int retry_count = 0;
 
 	if (!enc) {
 		/* Set the shared (decrypted) bits: */
@@ -718,12 +719,51 @@ static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
 		end   |= cc_mkdec(0);
 	}
 
-	/*
-	 * Notify the VMM about page mapping conversion. More info about ABI
-	 * can be found in TDX Guest-Host-Communication Interface (GHCI),
-	 * section "TDG.VP.VMCALL<MapGPA>"
-	 */
-	if (_tdx_hypercall(TDVMCALL_MAP_GPA, start, end - start, 0, 0))
+	while (retry_count < max_retries_per_page) {
+		struct tdx_hypercall_args args = {
+			.r10 = TDX_HYPERCALL_STANDARD,
+			.r11 = TDVMCALL_MAP_GPA,
+			.r12 = start,
+			.r13 = end - start };
+
+		u64 map_fail_paddr;
+		u64 ret = __tdx_hypercall_ret(&args);
+
+		if (ret != TDVMCALL_STATUS_RETRY)
+			return !ret;
+		/*
+		 * The guest must retry the operation for the pages in the
+		 * region starting at the GPA specified in R11. R11 comes
+		 * from the untrusted VMM. Sanity check it.
+		 */
+		map_fail_paddr = args.r11;
+		if (map_fail_paddr < start || map_fail_paddr >= end)
+			return false;
+
+		/* "Consume" a retry without forward progress */
+		if (map_fail_paddr == start) {
+			retry_count++;
+			continue;
+		}
+
+		start = map_fail_paddr;
+		retry_count = 0;
+	}
+
+	return false;
+}
+
+/*
+ * Inform the VMM of the guest's intent for this physical page: shared with
+ * the VMM or private to the guest.  The VMM is expected to change its mapping
+ * of the page in response.
+ */
+static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
+{
+	phys_addr_t start = __pa(vaddr);
+	phys_addr_t end   = __pa(vaddr + numpages * PAGE_SIZE);
+
+	if (!tdx_map_gpa(start, end, enc))
 		return false;
 
 	/* shared->private conversion requires memory to be accepted before use */
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index 90ea813c4b99..9db89a99ae5b 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -24,6 +24,8 @@
 #define TDVMCALL_MAP_GPA		0x10001
 #define TDVMCALL_REPORT_FATAL_ERROR	0x10003
 
+#define TDVMCALL_STATUS_RETRY		1
+
 #ifndef __ASSEMBLY__
 
 /*
-- 
2.25.1

Re: [PATCH v9 1/2] x86/tdx: Retry TDVMCALL_MAP_GPA() when needed

[Xiaoyao Li]

On 6/22/2023 3:13 AM, Dexuan Cui wrote:
> GHCI spec for TDX 1.0 says that the MapGPA call may fail with the R10
> error code = TDG.VP.VMCALL_RETRY (1), and the guest must retry this
> operation for the pages in the region starting at the GPA specified
> in R11.
> 
> When a fully enlightened TDX guest runs on Hyper-V, Hyper-V can return
> the retry error when set_memory_decrypted() is called to decrypt up to
> 1GB of swiotlb bounce buffers.

just out of curiosity, what size does Hyper-v handle at most in one call?

RE: [PATCH v9 1/2] x86/tdx: Retry TDVMCALL_MAP_GPA() when needed

[Dexuan Cui]

> From: Xiaoyao Li <xiaoyao.li@intel.com>
> Sent: Tuesday, July 18, 2023 7:31 PM
> ...
> On 6/22/2023 3:13 AM, Dexuan Cui wrote:
> > GHCI spec for TDX 1.0 says that the MapGPA call may fail with the R10
> > error code = TDG.VP.VMCALL_RETRY (1), and the guest must retry this
> > operation for the pages in the region starting at the GPA specified
> > in R11.
> >
> > When a fully enlightened TDX guest runs on Hyper-V, Hyper-V can return
> > the retry error when set_memory_decrypted() is called to decrypt up to
> > 1GB of swiotlb bounce buffers.
> 
> just out of curiosity, what size does Hyper-v handle at most in one call?

In my test, Hyper-V can process 1 to 9 pages in one call. Most of the time,
Hyper-V only processes 2 pages or 1 page, in one call.

Thanks,
Dexuan

[PATCH v9 2/2] x86/tdx: Support vmalloc() for tdx_enc_status_changed()

[Dexuan Cui]

When a TDX guest runs on Hyper-V, the hv_netvsc driver's netvsc_init_buf()
allocates buffers using vzalloc(), and needs to share the buffers with the
host OS by calling set_memory_decrypted(), which is not working for
vmalloc() yet. Add the support by handling the pages one by one.

Co-developed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
---
 arch/x86/coco/tdx/tdx.c | 35 +++++++++++++++++++++++++++++------
 1 file changed, 29 insertions(+), 6 deletions(-)

Changes in v2:
  Changed tdx_enc_status_changed() in place.

Changes in v3:
  No change since v2.

Changes in v4:
  Added Kirill's Co-developed-by since Kirill helped to improve the
    code by adding tdx_enc_status_changed_phys().

  Thanks Kirill for the clarification on load_unaligned_zeropad()!

Changes in v5:
  Added Kirill's Signed-off-by.
  Added Michael's Reviewed-by.

Changes in v6: None.

Changes in v7: None.
  Note: there was a race between set_memory_encrypted() and
  load_unaligned_zeropad(), which has been fixed by the 3 patches of
  Kirill in the x86/tdx branch of the tip tree.

Changes in v8:
  Rebased to tip.git's master branch.

Changes in v9:
  Added Kuppuswamy Sathyanarayanan's Reviewed-by.

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 746075d20cd2..c1a2423a8159 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -7,6 +7,7 @@
 #include <linux/cpufeature.h>
 #include <linux/export.h>
 #include <linux/io.h>
+#include <linux/mm.h>
 #include <asm/coco.h>
 #include <asm/tdx.h>
 #include <asm/vmx.h>
@@ -753,6 +754,19 @@ static bool tdx_map_gpa(phys_addr_t start, phys_addr_t end, bool enc)
 	return false;
 }
 
+static bool tdx_enc_status_changed_phys(phys_addr_t start, phys_addr_t end,
+					bool enc)
+{
+	if (!tdx_map_gpa(start, end, enc))
+		return false;
+
+	/* shared->private conversion requires memory to be accepted before use */
+	if (enc)
+		return tdx_accept_memory(start, end);
+
+	return true;
+}
+
 /*
  * Inform the VMM of the guest's intent for this physical page: shared with
  * the VMM or private to the guest.  The VMM is expected to change its mapping
@@ -760,15 +774,24 @@ static bool tdx_map_gpa(phys_addr_t start, phys_addr_t end, bool enc)
  */
 static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
 {
-	phys_addr_t start = __pa(vaddr);
-	phys_addr_t end   = __pa(vaddr + numpages * PAGE_SIZE);
+	unsigned long start = vaddr;
+	unsigned long end = start + numpages * PAGE_SIZE;
 
-	if (!tdx_map_gpa(start, end, enc))
+	if (offset_in_page(start) != 0)
 		return false;
 
-	/* shared->private conversion requires memory to be accepted before use */
-	if (enc)
-		return tdx_accept_memory(start, end);
+	if (!is_vmalloc_addr((void *)start))
+		return tdx_enc_status_changed_phys(__pa(start), __pa(end), enc);
+
+	while (start < end) {
+		phys_addr_t start_pa = slow_virt_to_phys((void *)start);
+		phys_addr_t end_pa = start_pa + PAGE_SIZE;
+
+		if (!tdx_enc_status_changed_phys(start_pa, end_pa, enc))
+			return false;
+
+		start += PAGE_SIZE;
+	}
 
 	return true;
 }
-- 
2.25.1

Re: [PATCH v9 0/2] Support TDX guests on Hyper-V (the x86/tdx part)

[Wei Liu]

On Wed, Jun 21, 2023 at 12:13:15PM -0700, Dexuan Cui wrote:
> The two patches are based on today's tip.git's master branch.
> 
> Note: the two patches don't apply to the current x86/tdx branch, which
> doesn't have commit 75d090fd167a ("x86/tdx: Add unaccepted memory support").
> 
> As Dave suggested, I moved some local variables of tdx_map_gpa() to
> inside the loop. I added Sathyanarayanan's Reviewed-by.
> 
> Please review.
> 
> FWIW, the old versons are here:
> v8: https://lwn.net/ml/linux-kernel/20230620154830.25442-1-decui@microsoft.com/
> v7: https://lwn.net/ml/linux-kernel/20230616044701.15888-1-decui%40microsoft.com/
> v6: https://lwn.net/ml/linux-kernel/20230504225351.10765-1-decui@microsoft.com/
> 
> Dexuan Cui (2):
>   x86/tdx: Retry TDVMCALL_MAP_GPA() when needed
>   x86/tdx: Support vmalloc() for tdx_enc_status_changed()
> 
>  arch/x86/coco/tdx/tdx.c           | 87 ++++++++++++++++++++++++++-----
>  arch/x86/include/asm/shared/tdx.h |  2 +
>  2 files changed, 77 insertions(+), 12 deletions(-)

Dexuan, do you expect these to go through the Hyper-V tree?

Thanks,
Wei.

> 
> -- 
> 2.25.1
> 

RE: [PATCH v9 0/2] Support TDX guests on Hyper-V (the x86/tdx part)

[Dexuan Cui]

> From: Wei Liu <wei.liu@kernel.org>
> Sent: Wednesday, June 28, 2023 11:06 AM
> To: Dexuan Cui <decui@microsoft.com>
> Subject: Re: [PATCH v9 0/2] Support TDX guests on Hyper-V (the x86/tdx
> part)
> 
> On Wed, Jun 21, 2023 at 12:13:15PM -0700, Dexuan Cui wrote:
> > The two patches are based on today's tip.git's master branch.
> >
> > Note: the two patches don't apply to the current x86/tdx branch, which
> > doesn't have commit 75d090fd167a ("x86/tdx: Add unaccepted memory
> support").
> >
> > As Dave suggested, I moved some local variables of tdx_map_gpa() to
> > inside the loop. I added Sathyanarayanan's Reviewed-by.
> >
> > Please review.
> > ...
> > Dexuan Cui (2):
> >   x86/tdx: Retry TDVMCALL_MAP_GPA() when needed
> >   x86/tdx: Support vmalloc() for tdx_enc_status_changed()
> >
> >  arch/x86/coco/tdx/tdx.c           | 87
> ++++++++++++++++++++++++++-----
> >  arch/x86/include/asm/shared/tdx.h |  2 +
> >  2 files changed, 77 insertions(+), 12 deletions(-)
> 
> Dexuan, do you expect these to go through the Hyper-V tree?
> 
> Thanks,
> Wei.

I suppose Dave and/or other x86 folks would like the 2 patches to go
through the tip tree if the patches look good. 

Hi Dave, any comments on the patches?

Thanks,
Dexuan

RE: [PATCH v9 0/2] Support TDX guests on Hyper-V (the x86/tdx part)

[Dexuan Cui]

> From: Dexuan Cui <decui@microsoft.com>
> Sent: Wednesday, June 28, 2023 11:45 AM
> To: Wei Liu <wei.liu@kernel.org>
> ...
> > From: Wei Liu <wei.liu@kernel.org>
> > Sent: Wednesday, June 28, 2023 11:06 AM
> > To: Dexuan Cui <decui@microsoft.com>
> > Subject: Re: [PATCH v9 0/2] Support TDX guests on Hyper-V (the x86/tdx
> > part)
> >
> > On Wed, Jun 21, 2023 at 12:13:15PM -0700, Dexuan Cui wrote:
> > > The two patches are based on today's tip.git's master branch.
> > >
> > > Note: the two patches don't apply to the current x86/tdx branch, which
> > > doesn't have commit 75d090fd167a ("x86/tdx: Add unaccepted memory
> > support").
> > >
> > > As Dave suggested, I moved some local variables of tdx_map_gpa() to
> > > inside the loop. I added Sathyanarayanan's Reviewed-by.
> > >
> > > Please review.
> > > ...
> > > Dexuan Cui (2):
> > >   x86/tdx: Retry TDVMCALL_MAP_GPA() when needed
> > >   x86/tdx: Support vmalloc() for tdx_enc_status_changed()
> > ...
> > Dexuan, do you expect these to go through the Hyper-V tree?
> >
> > Thanks,
> > Wei.
> 
> I suppose Dave and/or other x86 folks would like the 2 patches to go
> through the tip tree if the patches look good.
> 
> Hi Dave, any comments on the patches?

Hi Dave, would you please take a look at the 2 patches?

The patches have got Reviewed-by/Acked-by from Kirill, Sathyanarayanan
and Michael.
The patches can still apply cleanly on today's tip tree's master branch.
 
Thanks,
Dexuan

RE: [PATCH v9 0/2] Support TDX guests on Hyper-V (the x86/tdx part)

[Dexuan Cui]

> From: Dexuan Cui
> Sent: Monday, July 10, 2023 10:21 AM
> To: Dexuan Cui <decui@microsoft.com>; Wei Liu <wei.liu@kernel.org>;
> dave.hansen@intel.com; dave.hansen@linux.intel.com; bp@alien8.de;
> kirill.shutemov@linux.intel.com
> Cc: ak@linux.intel.com; arnd@arndb.de; brijesh.singh@amd.com;
> dan.j.williams@intel.com; Haiyang Zhang <haiyangz@microsoft.com>;
> hpa@zytor.com; jane.chu@oracle.com; KY Srinivasan <kys@microsoft.com>;
> linux-arch@vger.kernel.org; linux-hyperv@vger.kernel.org; luto@kernel.org;
> mingo@redhat.com; peterz@infradead.org; rostedt@goodmis.org;
> sathyanarayanan.kuppuswamy@linux.intel.com; seanjc@google.com;
> tglx@linutronix.de; tony.luck@intel.com; x86@kernel.org; Michael Kelley
> (LINUX) <mikelley@microsoft.com>; linux-kernel@vger.kernel.org; Tianyu Lan
> <Tianyu.Lan@microsoft.com>; rick.p.edgecombe@intel.com
> Subject: RE: [PATCH v9 0/2] Support TDX guests on Hyper-V (the x86/tdx part)
> 
> > From: Dexuan Cui <decui@microsoft.com>
> > Sent: Wednesday, June 28, 2023 11:45 AM
> > To: Wei Liu <wei.liu@kernel.org>
> > ...
> > > From: Wei Liu <wei.liu@kernel.org>
> > > Sent: Wednesday, June 28, 2023 11:06 AM
> > > To: Dexuan Cui <decui@microsoft.com>
> > > Subject: Re: [PATCH v9 0/2] Support TDX guests on Hyper-V (the x86/tdx
> > > part)
> > >
> > > On Wed, Jun 21, 2023 at 12:13:15PM -0700, Dexuan Cui wrote:
> > > > The two patches are based on today's tip.git's master branch.
> > > >
> > > > Note: the two patches don't apply to the current x86/tdx branch, which
> > > > doesn't have commit 75d090fd167a ("x86/tdx: Add unaccepted
> memory
> > > support").
> > > >
> > > > As Dave suggested, I moved some local variables of tdx_map_gpa() to
> > > > inside the loop. I added Sathyanarayanan's Reviewed-by.
> > > >
> > > > Please review.
> > > > ...
> > > > Dexuan Cui (2):
> > > >   x86/tdx: Retry TDVMCALL_MAP_GPA() when needed
> > > >   x86/tdx: Support vmalloc() for tdx_enc_status_changed()
> > > ...
> > > Dexuan, do you expect these to go through the Hyper-V tree?
> > >
> > > Thanks,
> > > Wei.
> >
> > I suppose Dave and/or other x86 folks would like the 2 patches to go
> > through the tip tree if the patches look good.
> >
> > Hi Dave, any comments on the patches?
> 
> Hi Dave, would you please take a look at the 2 patches?
> 
> The patches have got Reviewed-by/Acked-by from Kirill, Sathyanarayanan
> and Michael.
> The patches can still apply cleanly on today's tip tree's master branch.
> 
> Thanks,
> Dexuan

Hi Dave, kindly ping.